Mobile wireless communications device have advanced radio frequency (RF) processing circuits and receive or transmit radio communications signals typically using modulation schemes with In-phase (I) and Quadrature (Q) modulation and demodulation circuits that sometimes create linearity issues with power amplifiers and sometimes suffer poor antenna match. This can cause some degradation of TRP (total radiated power) and raise harmonic interference issues because of the higher non-linearity of a power amplifier, as an example.
Commonly assigned and copending patent application Ser. No. 12/173,045 filed Jul. 15, 2008, the disclosure which is hereby incorporated by reference in its entirety, addresses some of these issues and uses a mobile wireless communications device having a housing and antenna mounted within the housing. Radio frequency (RF) circuitry is carried within the housing, such as typically on at least one circuit board. It includes a transceiver connected to the antenna through which RF communication signals are transmitted and received. A processor is operative with the RF circuitry. A transceiver includes an In-phase and Quadrature (I/Q) Modulation and Power Amplification circuit and includes an In-phase (I) circuit having an In-phase signal input and a modulator mixer and power amplifier circuit that receives the In-phase signal and amplifies the In-phase signal. A Quadrature (Q) circuit includes a Quadrature signal input and a modulator mixer and power amplifier circuit that receives the Quadrature signal and amplifies the Quadrature signal. A power combiner receives the separately amplified In-phase and Quadrature signals and sums and outputs the signals as a combined I and Q signal.
This type of circuit described in the incorporated by reference '045 application provides an IQ modulation and power amplification circuit with respective power amplifier circuits in each of the I and Q circuits. It allows greater control over any power amplifier driver and/or power amplifier biasing, even when using either open loop systems or the larger or smaller closed loop systems. It is possible for the quadrature hybrid power combiner to be tolerable to the mismatch of antenna load impedance and give greater reflectivity for phase and frequency modulation, allowing efficient amplitude modulation to occur by changing the bias of the power amplifier circuits for each of the I and Q circuits and give greater flexibility and circuit function.
It has been found that greater improvements in this circuit are desirable concerning linearity with respect to I and/or Q power amplifiers and I and Q amplitude and phase imbalance issues. It would also be advantageous to address efficiency issues of the I and Q power amplifiers when using a different radio frequency (RF) output power level.